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Torsion Analysis - Wind vs. Seismic

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In flexible diaprhagm analysis (FDA) I typically analyze for the worst case 
condition due to wind or seismic in each line of shear. I am not sure how 
this is addressed in torsional analysis. It was my intent to take the 
conservative total shear to the structure at each level due to the 
combination of wind and seismic that governs and apply this load to the 
diaphragm in the rigid diaphragm analysis (RDA). 
In a previous discussion with another engineer I was advised that this was 
overly conservative and that it would also not yield correct distribution of 
shear by stiffness. I was advised to determine the total shear to the 
structure from either wind or seismic and apply the worst condition to the 
entire diaprhagm area. He also suggested that I may want to run the torsional 
analysis twice - once for wind and once for seismic to determine where the 
worst conditon will occur.
This seems counterproductive since the purpose of the RDA is to determine the 
correct balance from the single force applied (wind or seismic). To "beef up" 
the panels were wind might govern would essentially unbalance the system.

It seems that my first assumption is more valid since the total combined load 
would be applied at one time at a given point (point of applied load) which 
would yield a truer distribution of shear by torsion. The load, although 
combined, would be uniformly distributed by torsional analysis rather than 
arbitrarily increased in isolated lines of shear resistance.

I hope I'm made this clear. Can anyone advise me what standards of practice 
dictate in RDA?

Dennis S. Wish PE